R 中的 ARIMA 模型
David Stoffer
Professor of Statistics at the University of Pittsburgh

astsa 套件
library(astsa)
plot(jj, main = "Johnson & Johnson Quarterly Earnings per Share", type = "c")
text(jj, labels = 1:4, col = 1:4)

library(astsa)
plot(globtemp, main = "Global Temperature Deviations", type= "o")

library(xts)
plot(sp500w, main = "S&P 500 Weekly Returns")

迴歸:$Y_i = \beta X_i + \epsilon_i$,其中 $\epsilon_i$ 為白雜訊
白雜訊:
自我迴歸:$X_t = \phi X_{t-1} + \epsilon_t \ $($\epsilon_t$ 為白雜訊)
移動平均:$\epsilon_t = W_t + \theta W_{t-1} \ $($W_t$ 為白雜訊)
ARMA:$X_t = \phi X_{t-1} + W_t + \theta W_{t-1} \ $
R 中的 ARIMA 模型